Given historically high energy costs and the increasing difficulty to find replacement parts and lamps for obsolete magnetic ballast luminaires, many growers are looking to upgrade their lighting systems to reduce electrical consumption and operating costs; increase light intensity; improve crop health and yields; and/or take advantage of energy efficiency rebate programs.
Depending on each grower’s specific needs, a lighting upgrade could mean switching from HPS to LED luminaires; retrofitting older magnetic-ballast to new electronic ballast HPS luminaires; or upgrading to a hybrid (LED-HPS) lighting system which takes advantage of existing infrastructure—including HPS luminaires—but adds in new LEDs so growers get the best of both worlds.
HID to LED RETROFIT
One of the most common retrofits these days is growers replacing their legacy HPS luminaires with LED lighting. Now is a great time to do this, since many states, provinces and territories are offering rebate incentive programs for growers looking to install LEDs, as LEDs use much less energy to produce the light levels you need. In addition, LEDs offer growers more control, as they have a spectrum that is more efficient at converting photons into usable photosynthetic energy (referred to as photosynthetically active radiation or PAR). LEDs can also be dimmable, and they start up and power down more quickly than HPS luminaires—making it easier to manage and control your environment.
Choosing the right spectrum
When choosing LED lights for your retrofit, one important consideration is the type of spectrum you need. So, if you are thinking of switching from HID to LED lights, there are two options which are full/broad spectrum or red/blue spectrum. For many indoor grows, where they rely on artificial lights as their only source of light to grow plants, full or broad spectrum “white light” LEDs are the best option. This is because broad spectrum LEDs offer the plants a more complete spectrum—similar to natural sunlight. Broad spectrum LEDs are also better for workers because white light is easier to work under than blue/red light and makes plant assessment much easier. Broad spectrum “white” LED lights can be used for all stages of growth, including both vegetative and flowering growing stages.
Red and blue LEDs, where lights can appear pink or purple, are usually recommended for supplementary lighting in greenhouses, where plants are already receiving full spectrum sunlight from the outdoors. Since photosynthesis peaks in the blue and red spectrums, photons are more easily converted into photosynthetic energy at these wavelengths and therefore increase the overall energy efficiency of the lights.
Light Output and Uniformity
While an LED and HPS luminaire may emit the same PPFD (the amount of PAR light delivered to a square meter each second) many growers discover they need to install a greater number of LED luminaires vs. their HPS luminaires to achieve comparable light uniformity over the crop. This is because HPS luminaires use special reflectors to widely distribute the light over the crop surface, and the resulting crossover of the light helps achieve a layout with fewer luminaires and higher uniformity. LED luminaires do not use these reflectors so, typically most of the light is directed downwards meaning you generally require more LEDs to achieve the same light uniformity. Lighting manufacturers are heavily focused on addressing this limitation of LED technology. P.L. Light Systems recently set a new standard in LED lighting distribution with the TriPlane luminaire. The TriPlane is an LED luminaire that features independently adjustable LED modules for a precise and customizable light distribution.
Installation / Infrastructure Considerations
When you’re retrofitting your legacy lighting system, you also need to pay attention to any potential installation and infrastructure costs. Depending on your building design, you may need to install additional tracks to hang the LED luminaires to ensure uniform light distribution over the crop. A light plan, designed specifically to your application, will take these things into consideration to ensure you have the highest uniformity. In addition, the distance from the luminaire to the crop canopy should also be considered when making the switch.
You should always review your electrical infrastructure with your electrical designer in advance of transitioning to an LED lighting system. You will likely find that LEDs draw less power than HIDs, so an existing infrastructure that can support HID should be able to accommodate LED luminaires. However, if you are currently operating a 400W or other lower wattage HID system, that infrastructure may not be sufficient to power higher output LED luminaires and an upgrade and/or retrofit may be necessary. As long as you work with a lighting company that provides professional light plan you will be aware of any up front costs or additional electrical work you may need to plan for before moving ahead with a new lighting system.
Radiant vs. Convection Heat
Another important consideration is that the heat generated from HPS lights is often used to help offset heating costs in cold climate regions. In a 2021 study by Wageningen University, they set out to see how much energy is saved with an LED system versus an HPS system in a greenhouse application, when considering additional heating costs. They found that LEDs will reduce energy consumption for lighting by around 40%, but will increase heating requirements by 25%, making the total energy savings around 15%. So, the financial benefits of a transition to LEDs will depend on the energy and environmental costs associated with the application. This study helped demonstrate that in order to understand the true energy savings of LEDs, you must consider the entirety of your operation and include other areas of energy usage that can be affected by a switch in lighting technologies.
HYBRID LED-HPS LIGHTING SYSTEM
For growers who aren’t ready to make a full transition to an LED lighting system, a hybrid lighting system may be the ideal solution, and one that’s becoming an increasingly popular way to light CEA crops. By choosing to install an LED-HPS system, growers can keep their existing infrastructure, including some HPS luminaires, and can then install additional LEDs onto the existing track/truss. Hybrid lighting systems can be used for vine crops, cannabis, leafy greens and ornamentals and can be used in both greenhouse and indoor applications.
One reason a hybrid lighting system is so popular is that it allows growers to take advantage of the heat from the HPS luminaires during winter, while extending the season into early fall and spring with LEDs. Another key advantage is that by adding LEDs to your HPS system, you will enjoy some energy savings as the LEDs use less electricity but produce the same amount (or more) of light. A hybrid installation also allows for a quicker payback period, and growers can still take advantage of the financial rebate programs offered in Canada and the U.S.
LEGACY MAGNETIC HID to ELECTRONIC HPS RETROFIT
Well-maintained HID luminaires can last for decades. In fact, P.L. Light Systems has customers who are still running luminaires they installed 10 – 15 years ago – sometimes even longer than that. Finding replacement lamps and other parts like capacitors and ignitors, however, are becoming very difficult, if not impossible, to find. That’s because this old, magnetic ballast technology is now considered obsolete, so the component manufacturers are no longer making these parts. So, if this is your scenario, you really can’t put off upgrading your lighting system any longer.
That doesn’t necessarily mean you have to invest in LED technology to reap the benefits of improved lighting technology. HPS luminaires have come a long way in their 40+ years on the market, and there is a reason they remain a very popular type of horticultural lighting. Many growers are accustomed to growing under HPS and are reluctant to change what works for them. Additionally, many crops including tomatoes, cucumbers, flowers and cannabis grow very well under HPS conditions.
One the best parts of newer HPS technologies, is that they can deliver the same amount of light (or more) with fewer luminaires than older legacy lighting. This is due to their higher wattage, increased light intensity and improved reflector technology which helps spread light further. Electronic ballasts make it simple for growers to start up their luminaires and make maintenance and repairs much faster and easier. In addition, finding compatible lamps for new double-ended HPS luminaires is very easy and installation is much more straightforward.
An additional advantage of upgrading to electronic HPS luminaires, is that you should not require any major changes to your mounting and/or electrical infrastructure. We have worked with many growers over the last few years who have seen huge improvements in their business due to retrofitting with electronic ballast luminaires, including Burnaby Lake Greenhouses and the Houweling’s Group.
One consideration if you’re considering investing in new HPS luminaires, is the proposed Canadian legislation to ban the manufacture and import of HPS horticultural lamps by the end of 2028 and the sale of HPS horticultural lamps by the end of 2031, as part of Canada’s commitment to the Minamata Convention on Mercury. Although the USA has also signed this global treaty, and did federally ban all “general service” incandescent lamps, effective August 1st, 2023; they ultimately issued an exemption for lamps that are used for horticultural / plant growth purposes – leaving it to each state to issue their own guidelines. For example California, known to have the strictest energy-saving measures written into their codes, issued their Title 24 energy efficiency standards on January 1st, 2023 which include minimum efficacy requirements for greenhouse (PPE ≥ 1.7 μmol/J) & indoor (PPE ≥ 1.9 μmol/J) applications – which are in line with the current high-output, high-quality double-ended HPS lamps.
One of the greatest advantages of working with P.L. Light Systems is that we manufacture both LED and HID technologies and offer complete hybrid solutions. We also locally stock and sell replacement parts and lamps at highly competitive pricing. What this means for the grower, is that we can help assess all options when it comes to maintaining or upgrading their lighting systems. This allows us to provide complete lighting options that take into account the exact goals the grower wants to achieve with whatever type of lighting they want to use.
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